This invention generally relates to lifts for watercraft, and more particularly, to floating watercraft lifts capable of raising and lowering a watercraft.
A watercraft may encounter a variety of problems when a hull of the watercraft remains submerged in a lake, or other body of water, for a protracted period of time. For example, the watercraft may be subjected to significant physical damage when the hull is exposed to strong wave activity resulting from weather conditions or the wakes of passing watercraft. This damage generally occurs where the hull of the watercraft repeatedly contacts a stationary object such as a portion of a dock, floating debris, or even another watercraft that is docked nearby. Further, while the watercraft hull remains in the water, the exterior hull surfaces of the watercraft may acquire significant amounts of marine growth that may impair the performance of the watercraft, and superficially damage the hull surfaces if not frequently removed.
In response to these difficulties, watercraft lifting devices have been developed that generally include a user-actuated mechanical lifting mechanism that is positioned below the watercraft to lift it from the water and support it above the surface of the water when the watercraft is not in use. When it is desired to refloat the watercraft, the user is able to release the mechanical lifting mechanism to lower the watercraft into the water. The watercraft lift is therefore a particularly convenient solution to the foregoing difficulties, since the watercraft may be quickly removed from the water during periods of non-use, and refloated when desired, with minimal human effort.
One category of known watercraft lifts include a mechanical lifting mechanism that is attached to a support platform having columns, or other supports, that that extend downwardly from the platform to the bottom of a body of water. When the watercraft is supported by the lifting mechanism, the resulting load is transferred from the lifting mechanism to the bottom by the columns attached to the support platform. U.S. Pat. No. 4,895,479, for example, describes a watercraft lift that includes a lifting mechanism that is positioned below the water surface that is supported by a plurality of posts that are anchored to the bottom. Similarly, U.S. Pat. No. 5,184,914 also describes a lift having a submerged lifting mechanism supported above the bottom by a plurality of posts that are attached to the bottom.
One disadvantage present in this category of watercraft lifts is that they require that the watercraft lift be maintained in a fixed location, since the column supports are driven into the bottom of the body of water, or are otherwise attached to fixed anchor positions located on the bottom. Further, watercraft lifts that are attached to the bottom generally cannot accommodate significant water level variations that may exist in the body of water. Such variations in water level may be due, for example, to tidal activity if the water craft is maintained in a marine environment, or due to the storage or release of water from a nearby dam if the watercraft is maintained in a lake or river adjacent to the dam.
Another category of watercraft lifts includes one or more enclosed chambers that may be selectively inflated to lift the watercraft from the water surface. For example, U.S. Pat. No. 5,860,379 describes a watercraft lift having air chambers fabricated from a flexible, impermeable fabric that are positioned beneath the watercraft. A network of hoses and valves connects an air inflation device to the enclosed chambers. As inflation air is provided to the enclosed chambers, water is expelled from the chambers thus lifting the watercraft from the water surface. A similar watercraft lift is described in U.S. Pat. No. 4,750,444, which includes a platform for supporting the watercraft that has a downwardly extending lifting skirt having an open bottom that is connected to an air inflation device. By providing inflation air to the skirt, the platform that supports the watercraft may be raised above the water surface.
Although the operation of the foregoing watercraft devices is not generally limited by water level variations, other disadvantages nevertheless exist. For example, in order to provide sustained support for the watercraft, the inflation chambers must be capable of sealably containing the inflation air for prolonged periods of time. If the inflation chambers or the inflation system cannot sealably contain the inflation air, the watercraft will not be maintained in an elevated position above the water surface.
Still another category of watercraft lifts include one or more sealed floatation chambers that are moveable relative to the watercraft to raise and lower the watercraft. For example, U.S. Pat. No. 5,131,342 discloses a watercraft lift having a pair of spaced-apart floatation chambers with watercraft support beams positioned between the floatation chambers. The floatation chambers are translated in a vertical direction to partially raise and lower the watercraft. In order to fully submerge the support beams to receive the watercraft, however, the floatation chambers must be at least partially flooded with water. Correspondingly, when the watercraft lift is to raise the watercraft, water must be pumped from the floatation chambers to establish sufficient buoyancy to lift the watercraft from the water. Since the foregoing device is unable to effect a sufficient change in buoyancy by mechanically re-positioning the floats, it is therefore subject to the shortcomings described above since it relies on sealably containing inflation air within floatation chambers.
Accordingly, there is a need in the art for a watercraft lift to support a watercraft that is not limited by variations in water depth, and does not require support from the bottom of a body of water. Further, there is a need for a watercraft lift that does not require floatation chambers that must be inflated with air and/or flooded with water in order to develop sufficient changes in buoyancy to raise and lower the watercraft.
The present invention is generally directed to a floating watercraft lift capable of raising and lowering a watercraft, and more particularly to a floating watercraft lift that does require support from a bottom of a body of water and is capable of operation in water that may vary in depth. The watercraft lift may be positioned in a standard-sized boat slip, as well as in double-wide slips, where two such lifts may be used side by side, or only one lift may be used without impeding the berthing of a second watercraft in the slip. The watercraft lift may also be used separate from a slip or fixed dock, and may be anchored to a buoy, or other mooring devices, and may be conveniently and easily relocated to different locations when desired.
In one aspect of the invention, the watercraft lift includes a pair of longitudinally extending and approximately parallel floats with an apparatus for supporting and lifting a watercraft extending between the floats. When the watercraft lift is positioned in a lowered position, the apparatus is submerged and each of the floats is in a first orientation and partially submerged. When the watercraft enters the watercraft lift, it may be guided onto the lift by a pair of at least partially submerged and longitudinally extending bunks that extend lengthwise on either side of the watercraft. When the watercraft has moved a sufficient distance along the length of the lift, the watercraft contacts the bunks. The apparatus may then be activated to move the watercraft lift to a raised position. The apparatus moves the floats downwardly and inwardly towards the watercraft, so that the floats become further submerged in the water. The buoyancy of the submerging floats thus lifts the lift apparatus and the watercraft above the water surface.